Problem - Asymmetric routing with two gateways

[HatalaTitla48]

Hi, I have old box with multiple vlans/subnets connected to switch. On same network/vlan I have connected new opnbox to the same switch and created in opnsense direct route(192.168.12.0/24 192.168.12.1 - far gateway) to the subnet 192.168.12.0/24 on old box(it has own gw on 192.168.12.1).
Now comunication and routing works ok between boxes and subnets until I try access from openvpn client subnet(192.168.202.0/27) to the 192.168.12.0/24. On the old box i did put direct route to the networks on opnbox "route add -net 10.88.1.0 netmask 255.255.255.0 gw 10.88.1.254 eth5" and "route add -net 192.168.202.0 netmask 255.255.255.224 gw 10.88.1.254 eth5". Both work ok, I get even response from ip delegated to vpn user on its notebook. But ping from notebook to 192.168.12.1 is without response.
Ive been looking for a cause and found out about asymetric routing, both boxes have different gw. Ive tried on opnbox outbound(snat) NAT, to mask opnbox gw 10.88.1.254 for 192.168.12.5(ip of opnbox interface connecting to oldbox) but so far without success. Probably easy fix...where I should look?

Thx.